Our long term objective is to understand the organization and expression of regulatory and structural gene systems from simple organisms. We intend to develop and use various molecular cloning techniques for the study of gene systems from prokaryote and simple eukaryote cells (yeast and Drosophila). We will study the expression of genes introduced on amplifying DNA vectors into a prokaryote host. Biochemical and genetic methods, designed to permit the alteration and control of gene expression from these hybrid DNA plasmids will be investigated. It is anticipated that specific regions of chromosomal DNA, along with the corresponding gene products, will be made available in quantity by these techniques. The cloning and amplification of transfer RNA gene systems from E. coli, yeast and Drosophila will be a major emphasis of the proposed work, with the intent of studying the arrangement and transcription of these genes. In addition, however, several key E. coli gene systems, such as those involved in DNA replication, RNA transcription and gene regulation, will be investigated by molecular cloning techniques. Critical experiments will be carried out to determine if meaningful expression of yeast and Drosophila gene systems can be obtained from hybrid plasmids in suitable bacterial host cells. Hybrid plasmids will be biochemically restructured to bring eukaryotic genes under the control of bacterial promoters and regulatory elements.